Various embodiments disclosed herein relate to devices that suppress transient voltage events which could potentially damage sensitive connected equipment and more specifically to a non-degrading surge suppressor and method for detecting and suppressing surge events.
A conventional series mode device for suppressing transient voltage events typically uses an L-C (inductor-capacitor) filter, where the capacitor is located within a bridge rectifier circuit and thereby prevents charge from being transferred back to the line once the charge has been stored in the capacitor. The conventional device performs surge detection after the initial inductor of the L-C filter and after the bridge rectifier. Specifically, the conventional device detects a surge event by monitoring the charge of a single capacitor within the bridge rectifier circuit. The capacitor is held charged to the peak level of the incoming AC (Alternating Current) line voltage, and when a surge event occurs, additional discharged capacitors are switched into the circuit.
Conventional methods for surge detection rely on the detection of a surge event after the series inductor of an L-C filter. Due to the nature of L-C filters, a conventional device does not detect or suppress surges until after the voltage at the output line has already begun to rise, which could potentially damage any equipment connected to the output line. Additionally, a capacitor within the bridge rectifier circuit is kept charged to the peak level of the incoming AC line. Because capacitor lifespan is dependent on a working voltage of the capacitor, a higher working voltage equates to a shorter lifespan. Since the capacitor in a conventional device is always held near the peak level of the line voltage, special attention must be paid to the rated working voltage of the capacitor to mitigate the possibility of a long duration voltage swell. For example, for a 120VAC circuit in the United States, the capacitor would be held at a nominal voltage of about 170VDC during normal operation. One of ordinary skill in the art could surmise from best practices that a capacitor with a working voltage of 250VDC could be used. However, in the event of a swell in voltage, for example, 200VAC, the voltage across the capacitor would rise to about 283VDC, well above the rated working voltage of the capacitor. To protect the conventional surge suppressing device during high voltage swells, the conventional device typically employs a crowbar circuit before the L-C filter where the incoming line is disconnected from the capacitor in the bridge rectifier circuit until the voltage swell has passed or manually reset by an operator.